Rear Break Master Cylinder

[IICYCLE]

I installed the fj 1200-1100 rear master cylinder kit 2 years ago on my rd400 and have found that when the rear brake is applied the master cylinder shaft does not want to return to its resting position. I have disassembled the master cylinder and it is nice and clean. the return spring seems to be good. I applied some rubber friendly grease to the rubber seal and the shaft returns easily. Should i leave it at that or is there another issue perhaps the seal is swollen. Im using synthetic fluid.

Thanks

[SoCal250]

Sounds like the bleed port may be clogged. See the info in Chuck's post: https://www.2strokeworld.net/forum/index.php?topic=1621.0
I usually run a piece of copper wire into the hole to make sure it's clear. Then run it through my ultrasonic

[IICYCLE]

Ya I seen Chucks post and made sure the small hole was clear but the master cylinder plunger is still very slow to return to its resting position. The master cylinder bore seems good but maybe try to clean with a green scratch pad ?

[pidjones]

Ya I seen Chucks post and made sure the small hole was clear but the master cylinder plunger is still very slow to return to its resting position. The master cylinder bore seems good but maybe try to clean with a green scratch pad ?

Too course for me. Maybe 1200 grit with isopropyl alcohol to flush and lubricate the abrasive - and make sure the piston cups are on the correct way and lubricated with brake fluid.